High start clipping causing dashed edges in 3d view?
its because Graphic cards Render the depth to a 16 - 32 Bit Depth Buffer where the start Clipping is 0 and the end Clipping is the max Value. But that Depth Buffers are only 32 Bit and 1e-40 is equal to 2e-40 there because its rounded.
And when that happens the Graphics card can't figure out whats in the front and whats behind. You can also see this if you add 2 Planes is the exact same spot and then color them differently. You can even experiment with the distance between that planes and the clipping.